Heat resistant cast iron of valve material

Heat resistant cast iron of valve material

This scale defines the technical requirements, test methods, maintenance rules, marking and quality certification, rust prevention, packaging and storage requirements of heat resistant cast iron. The geometry and size of the casting should conform to the requirements of the drawing. The dimensional tolerance and machining allowance shall be in accordance with GB/T6414 and the weight deviation shall be in accordance with GB/T 11351. The metallographic structure of heat-resistant cast iron shall be defined according to GB/T 9441 and GB/T 7216, and detailed requirements shall be agreed upon by both parties. The matrix structure of silicon heat resistant cast iron is mainly ferrite.

1 range

This scale defines the technical requirements, test methods, maintenance rules, marking and quality certification, rust prevention, packaging and storage requirements of heat resistant cast iron.

This scale is suitable for sand forging or heat resistant cast iron castings with heat conductivity similar to sand mold and working below 1100℃.

2 Normative reference files

The terms in the following documents become terms of this scale by reference to this scale. For dated citations, all subsequent amendments (excluding erratum) or revisions are not applicable to this scale. However, parties to agreements under this scale are encouraged to investigate the availability of *** versions of these documents. For undated references, the *** version is applicable to this scale.
3 Technical Requirements

3. Grade and chemical composition of heat-resistant cast iron

The designation method of heat-resistant cast iron conforms to the demarcation of GB/T5612, which is divided into 11 grades.

The grade and chemical composition of heat-resistant cast iron are shown in Table 1.

Table 1. Grade and chemical composition of heat-resistant cast iron

3.2 Geometric dimensions, machining allowance and weight tolerance

The geometry and size of the casting should conform to the requirements of the drawing. The dimensional tolerance and machining allowance shall be in accordance with GB/T6414 and the weight deviation shall be in accordance with GB/T 11351.

3.3 Surface Quality

3.3.1 Casting surface roughness shall conform to the delineation of GB/ T6061.1, and the scale grade shall be agreed by both parties.

3.3.2 The castings shall be cleaned up, the redundant parts shall be trimmed, and the residue of pouring riser, core bone, clay sand and inner cavity shall be removed. Castings shall comply with the requirements of the buyer’s drawing, technical requirements or the order agreement between the two parties.

3.3.3 The form, number, size and position of the agreed defects on the casting, repairability and repair method shall be agreed by both parties.

3.4 Mechanical function

The mechanical properties of castings at room temperature shall conform to the delineation in Table 2, and the short-term high temperature tensile properties are shown in Appendix A

3.5 Heat Treatment

Generally, heat treatment should be carried out to remove residual stress for heat-resistant ductile iron of silicon and aluminum series. However, when the pearlite content of heat-resistant ductile iron of silicon key series is lower than 15%, heat treatment can not be carried out. For other brands, if required by the demander, the heat treatment to eliminate residual stress shall be carried out according to the premise of ordering.

The preconditions for the use of heat-resistant cast iron are shown in Appendix B

3.6 Metallographic structure

The metallographic structure of heat-resistant cast iron shall be defined according to GB/T 9441 and GB/T 7216, and detailed requirements shall be agreed upon by both parties. The matrix structure of silicon heat resistant cast iron is mainly ferrite.

3.7 Anti-oxidation, anti-growth function and coefficient of thermal expansion

At the service temperature, the uniform oxidation weight gain rate of heat-resistant cast iron is no more than 0.5 g/m2·h, and the growth rate is no more than 0.2%. The anti-oxidation and anti-growth function of heat-resistant cast iron and the coefficient of thermal expansion are not used as the basis for acceptance.

3.8 Special Requirements

If the demander has requirements for magnetic particle testing, ultrasonic testing, X-ray testing, etc., the demander and the demander shall negotiate and execute according to GB/T 9494, GB/T 7233 and GB/T 5677 respectively.

4 Test method

4.1 Chemical composition analysis

4.1.1 Chemical composition analysis can be carried out by conventional chemical analysis or photoelectric direct reading spectroscopic analysis.

4.1.2 Sampling methods for conventional chemical analysis shall be specified in GB/T 20066.

4.1.3 Spectrum sampling method shall be performed according to GB/T 5678 and GB/T 14203. The spectral analysis method shall be performed according to the specification of GB/T 20125.

4.1.4 Arbitrate analysis of carbon, silicon, manganese, sulfur and phosphorus in chemical composition is GB/T 20123 or GB/T223.69,GB/ T223.60 and GB/T respectively Execution of demarcations of 223.58 or GB/T223.64,GB/T223.3 or GB/T223.59 or GB/T223.61,GB/T223.68; Chromium, aluminum, aluminum arbitration analysis respectively according to GB/T223.11 or GB/T223.12, GB/T223.26, GB/T223.28 delimit the execution.

4.2 Mechanical function test

4.2.1 Room temperature mechanical function tests of HTRCr, HTRCr2, HTRSi5 and other grades, including the preparation of samples, shall be carried out according to the specification of GB/T228.

4.2.2 Mechanical tests of heat-resistant ductile iron and HTRCr16 at room temperature shall be carried out according to GB/T228.

4.2.3 The hardness of heat resistant cast iron shall be determined according to GB/T231.1.

4.2.4 Short-time high temperature tensile strength of heat-resistant cast iron shall be determined according to GB/T4338.

4. 3 Test block, sample

4.3.1 The shape and size of Y-shaped single cast test block used in the tensile test of QTRSi4,QTRSi5, QTR5i4Mo, QTRSi4Mo1,QTRA14Si4, QTRA15Si5 are shown in FIG.1 and Table 3 (the oblique line in FIG.1 is the location of the cut sample). Type B is generally selected. The test blocks in Appendix C may also be used. Shape and size of single cast easy cutting test block for QTRA122 and HTRCr16

4.3.2 The shapes and sizes of tensile samples used by heat-resistant ductile iron brands and HTRCr16 brands are shown in FIG.3 and Table 4.

4.3.3 Test blocks shall be filled with the same liquid iron as the casting and poured at the end of the process, and the cooling mode shall be as consistent as possible with the casting.

4.3.4 The packing temperature of test blocks shall not exceed 500 ° C

4.3.5 It is agreed to take the sample attached to the casting block or directly on the casting, and the acceptance value shall be agreed by both parties.

4.4 Oxidation Resistance and Growth Resistance Test The oxidation resistance and growth resistance test of heat resistant cast iron shall be carried out according to Appendix D and Appendix E.

4.5 Coefficient of Thermal Expansion test The test method of coefficient of thermal expansion is carried out in Appendix F.

4.6 Heat Treatment

In addition to removing the internal stress of the castings, if any other heat treatment is performed on the castings, the test blocks shall also be subjected to heat treatment in the same furnace or process.

Unit: millimeter

5 Acceptance Rules

5.1 Composition of the sampling batch

5.1.1 The castings produced by the unified mold shall constitute a sampling batch.

5.1.2 The bulk weight of each sample lot is 2000 kg of castings after cleaning. The sampling batch can be changed as agreed by both parties.

5.1.3 If the weight of a casting is greater than 2000 kg, a separate sampling batch shall be constituted.

5.1.4 In the event of a change in charge, a change in process premise or a change in the required chemical composition within a certain time period, all castings poured with molten iron continuously melted during that time period, regardless of how short the time period, shall be considered as one sample lot.

5.1.5 When large quantities of molten iron of a uniform grade are continuously melted, the relative mass of each sample lot shall not exceed the weight of castings poured within 2 hours.

5. 1.6 This batch of molten iron castings may be used as a sampling batch when the weight of molten iron is less than 2000 kg.

5.1.7 As agreed by both parties, several batches of castings can also be accepted in a group.

In this case, there should be other quality control methods in the production process, such as rapid chemical composition analysis, metallographic maintenance, nondestructive testing, fracture maintenance, etc., and indeed proved that the nodulation treatment is not chaotic, in line with the process requirements.

Note: For castings that have been heat-treated, the sample batch shall be uniformly sampled, unless the castings in the batch differ significantly in structure. In this case, these significantly dissimilar castings constitute a sample batch.

5.2 Sampling of Chemical Composition Each sampling batch shall be subjected to a chemical composition analysis, and the analysis results shall meet the requirements in Table 1. If the chemical composition is different, allow double the number of samples to be reanalyzed once, the sample is qualified only when it is fully qualified.

5.3 Casting size sampling

The size, geometry and surface roughness of the first castings and important castings should be checked on each piece. The method of spot check shall be agreed by both parties.

5.4 Sampling inspection of appearance quality

The appearance quality of castings should be visually inspected piece by piece.

5.5 Sampling and testing of mechanical properties, metallography, growth resistance The mechanical properties of heat resistant ductile iron at room temperature should be checked by batch. The mechanical properties of other heat-resistant cast iron at room temperature as well as the metallurgical structure, oxidation resistance and growth resistance of all brands shall be tested according to the premise of ordering. The mechanical properties of room temperature are accepted based on tensile strength. If hardness inspection is required before ordering, it should meet the requirements of Table 2. In order to ensure that the furnace or package number of the casting is the same as that of the test rod, the furnace or package number should be clearly marked on the non-important surface between the sample and the casting.

5.6 Evaluation of mechanical function test results

When inspecting the tensile strength, if the inspection result of the tensile sample fails to meet the requirements, and it is not caused by the reasons listed in 5.7, another two specimens from the unified batch can be taken for reinspection.

If the reinspection results meet the requirements, the material of this batch of castings is still qualified. If the reinspection result still fails to meet the requirements, the batch of castings will be preliminarily judged as the material division. At this time, one of the castings can be taken from the batch, and the body sample can be cut at the position agreed by both parties for mechanical testing. If the test results meet the requirements, the casting material can still be judged to be qualified; If the test result of the body sample still fails to meet the requirements, the ** finally determines that the casting material of this batch is split lattice.

5. 7 Validity of the test

If the test results do not meet the requirements, not because of the quality of the casting itself, but because of one of the following reasons, the test is invalid.

a) Improper loading of the sample on the testing machine or improper operation of the testing machine.

b) There are forging defects on the surface of the sample or improper cutting of the sample (such as the sample size, transition fillet, roughness does not meet the requirements, etc.).

c) Tensile specimen breaks outside the standard distance.

d) There are significant forging defects on the fracture of tensile specimen.

In such cases, a new sample shall be made from the uniform test block or the sample shall be reprocessed from the uniform batch of poured test block for retesting, and the result of the retesting shall replace the result of the invalid test.

5.8 Heat treatment of test blocks and castings

Unless there are special requirements, if the castings are supplied as cast and the mechanical function of the castings does not conform to this scale, the supplier may, with the consent of the Demander, heat treat the castings together with the test blocks and then re-test them. If the castings have been heat-treated and the mechanical function is divided, the supplier can re-heat the castings and the test blocks of the castings together. And submit again for acceptance. If the specimen processed from the heat treated test block is qualified, the batch is considered to be repeated heat treated

Part function conforms to this scale.

Repeated heat treatment for reinspection shall not exceed two times.

If there is no clear requirement on the position, size (size, height, convex and concave) and method of the mark, the supplier and the supplier shall agree. However, the marking shall not damage the casting quality. After the castings pass inspection and maintenance, the rust prevention, packaging and storage methods shall be agreed by both parties. There is enough gap between the samples placed in the furnace to ensure good contact between the air in the furnace and the sample surface. Two measuring screws can be installed at both ends of the sample, the dimensions of which are shown in Figure D.2. (If no measuring screws are needed, the end face of the sample can be plated with chromium or nickel…

Certificate of mark and quality

6. 1 The castings shall be marked by the supplier.

6. 2 If there is no clear requirement on the position, size (size, height, convex and concave) and method of the mark, both parties shall agree. However, the marking shall not damage the casting quality.

6. 3 The quality certificate of the supplier’s inspection seal shall be attached to the casting before delivery, and the contents of the certificate shall include the following contents:

a) Name or logo of the supplier;

b) Part number or order contract number;

C) Material brand;

d) Maintenance results;

e) Scale number.

Rust prevention, packaging and storage

7.1 The rust prevention, packaging and storage methods of the castings shall be agreed upon by both parties after the castings are checked and qualified.

7.2 For castings transported over long distances, both parties shall agree on packaging and means of transportation according to the transportation regulations.

Environmental protection, safety and legal and regulatory requirements

Both parties shall comply with the environmental protection, safety and laws and regulations of the relevant countries during production, acceptance, storage and transportation.

Test method for growth resistance of heat resistant cast iron

This method can be used to test the growth resistance of various heat resistant cast iron in high temperature air medium.

D.1 Basic requirements for testing equipment and premises against growth

D.1.1 The growth resistance test furnace shall meet the following requirements:

a) There is an automatic temperature adjustment device, the accuracy of which is 5℃;

b) The temperature difference between each point in the sample distribution zone in the furnace shall not exceed 5℃;

c) Maintain sufficient oxidation atmosphere in the furnace.

D.1.2 There is sufficient clearance between the samples placed in the furnace to ensure good contact between the air in the furnace and the surface of the samples.

D.1.3 After the sample is loaded into the furnace, the time when the temperature in the furnace reaches the specified temperature shall be regarded as the start of the test, and the time when the specified test period is over and the furnace stops working (or takes out the sample) shall be regarded as the end of the test.

D.2 Outside the sample